AW: pre-boot plugged SFP autoneg advertisement

[<markus.stockhausen@gmx.de>]

> Von: Andrew Lunn <andrew@lunn.ch> 
> Gesendet: Montag, 20. April 2026 19:58
> An: markus.stockhausen@gmx.de
> 
> > Sequence of events during boot is as follows:
> > 
> > - SFP module is already inserted (in my case 1G)
> > - phylink_sfp_config_phy() runs long before any network config starts
> > - OpenWrt netifd daemon starts and wants to configure the network
interfaces
> > - It reads current settings via ethtool ioctl and gets autoneg=off
> > - It writes basic config values via ethtool ioctl including autneg=off
> > - Later on it starts the interface and phylink_start() is issued
>
> I would say netifd is not optimal. I'm not sure we every agree to
> return the full ksetting on an interface which is admin down. Many
> driver don't even connect to the PHY until open is called, and so are
> likely to return -ENODEV. See phy_ethtool_set_link_ksettings().
>
> Could you look into the behaviour of netifd, especially if it gets
> -ENODEV during the first read. Does it try again after setting the
> interface up?

Netifd has no issues with linksettings reading/writing in admin state.
Getting a rc=0 it assumes that all values are filled, changes the needed
attributes and writes them back. I retested and think there might be a 
solution to avoid unneeded Ioctl access (see [1])

> If we know phylink is going to return a subset of the correct
> information when the interface is admin down, maybe it should return
> -ENODEV?

Or (stupid idea) phylink_ethtool_ksettings_set() should not accept all 
settings in this state. 

Thanks for your valuable input.

Markus

[1] https://github.com/openwrt/netifd/issues/76#issuecomment-4283478081